Al-Rahman, believed to be in his mid-30s, was a close confidant of bin Laden and once served as his emissary to Iran - a role which allowed him to move freely in and out of the Islamic Republic.

After Navy SEALs killed bin Laden, they found evidence of al-Rahman’s role as operational chief.

Born in Libya, al-Rahman joined bin Laden as a teenager in Afghanistan to fight the Soviet Union.

Defense Secretary Leon Panetta said last month thatal-Qaeda's defeat was within reach if the US could mount a string of successful attacks on the group's weakened leadership.

"Now is the moment, following what happened with bin Laden, to put maximum pressure on them, because I do believe that if we continue this effort we can really cripple al-Qaida as a major threat," Mr Panetta said.